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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: 74CustomDeluxe20 on April 23, 2013, 01:06:18 pm

Title: No Power
Post by: 74CustomDeluxe20 on April 23, 2013, 01:06:18 pm

Hi guys,
     I went out to start my truck yesterday a.m. and turned the key and nothing happened.  I had been towing a rental backhoe and was getting ready to return it.  I still had accessory power but hooked it up to a jump start just to eliminate that end of it.  My first thought was the safety neutral switch.  The truck is a 3spd with a granny gear.  But I am leaning toward ignition switch.  There is alot of play in the key/ignition and you can actually remove key and turn ignition.  Just looking for thoughts and suggestions.  Thanks in advance for your responses.
Regards,
Bob

Title: Re: No Power
Post by: mehunter1 on April 23, 2013, 01:24:40 pm

When you say accessory power, do you mean key on power?  Heater fan blows, lights come on, radio works, etc?  Just no spark on the crank, right?  Might your clutch not be engaging?

Title: Re: No Power
Post by: 74CustomDeluxe20 on April 23, 2013, 01:38:55 pm

That is very possible.....I do have heater, radio, fan, and lights.  My first thought was the NSS because I assumed it was clutch related, being that was the first time I towed anything of any substantial weight.  Thanks for the response!
Bob

Title: Re: No Power
Post by: Jason S on April 23, 2013, 08:23:12 pm

You can disconnect the wiring at the NSS and using a meter, see if there is power at the wiring harness connector.

If it is a malfunctioning switch, then a jumper wire across the harness terminal can bypass a malfunctioning NSS.

If there isn't power to the NSS switch, then you move further up the wiring harness to the ignition switch at the base of the column.

Title: Re: No Power
Post by: 74CustomDeluxe20 on April 24, 2013, 10:24:21 am

Thanks Jason....I appreciate it!
Bob

Title: Re: No Power
Post by: Jason S on April 26, 2013, 08:19:43 pm

Bob, I posted this here just in case you or others need to access the photos or information.

The Clutch NSS switch is attached to the Clutch Release Arm (Clutch Pedal) and anchored to a dash bracket. The NSS switch snaps into the clutch arm and has a plastic bolt and nut threaded into the dash bracket.  I've attached photos of the wiring diagram from a 1978 Chevy Truck Manual and photos of the NSS as actually installed on a 1974 Chevy Truck.  The photo point is from directly below the clutch pedal looking up. If you have the tubing for the LH dash vent in place (i.e., an A/C equipped truck), it may be difficult to see.

View of Right Hand Instrument Panel wiring (1978 Chevy Truck)
(https://lh3.googleusercontent.com/-mjeEoTGr7J0/UXsjoAfvT5I/AAAAAAAAAvg/InSgY7ej6eo/s800/DSC05219.JPG)

Closeup of Right Hand Instrument Panel wiring (1978 Chevy Truck)
(https://lh6.googleusercontent.com/-_JhU8qqD0s0/UXsjkgK0LeI/AAAAAAAAAvM/2sQSMN-5ua8/s800/DSC05221.JPG)

View from below of installed Clutch NSS switch as installed on 1974 Chevy Truck. The NSS is the white rectangular plastic part with the plastic arm that snaps into the clutch release arm. The portion of the NSS switch that bolts through the dash bracket is not seen, but when looking up should be apparent.  The white plug-in at a 90 degree to the NSS switch is the wiring harness.  This can be removed and jumpered if necessary to bypass the NSS.
(https://lh5.googleusercontent.com/-E7oqodkSAJM/UXsjhR1gHLI/AAAAAAAAAu8/ROMQSmDOk6A/s800/DSC05223.JPG)